Pyrotechnic disseminating system

ABSTRACT

The present application discloses a pyrotechnic formulation for disseminating insecticides such as Dursban and Ronnel brand insecticides manufactured by The Dow Chemical Company. The formulation comprises an oxidizing agent, a non-halogenated polyepoxide resin as fuel and binder, an auxiliary fuel such as thiuram disulfide, a cooling additive, and an effective amount of the insecticide to be disseminated.

nited States Patent ,Iankowiak et al.

[ 1 Dec. 24, 11974 PYIROTECHNIC DISSEMINATING SYSTEM Inventors: Erwin M. Jankowiak, Sanford; Earl Thomas Niles; George A. Lane, both of Midland, all of Mich.

Assignee: The Dow Chemical Company,

Midland, Mich.

Filed: Sept. 8, 1970 Appl. No.: 70,493

Related US. Application Data Continuation-impart of Ser. No. 709,916, March 4, 1968, abandoned.

US. Cl 424/42, 424/40, 424/41 Int. Cl C06d 3/00 Field of Search 424/40, 41, 42

References Cited UNITED STATES PATENTS 2,700,011 1/1955 Taylor H 424/40 2,969,334 1/1961 Steckler 260/25 2,991,220 4/1961 Bruce 424/200 3,044,929 1/1962 Bodo et al. 424/42 3,244,586 4/1966 Rigterink 424/200 3,314,835 4/1967 White et al. 424/40 3,391,036 7/1968 James et al. 424/40 3,467,558 9/1969 Wernette et al. 149/19 FOREIGN PATENTS OR APPLICATIONS 148,773 3/1949 Australia 424/42 Primary ExaminerFrederick E. Waddell Attorney, Agent, or FirmBruce M. Kanuch [57] ABSTRACT The present application discloses a pyrotechnic formulation for disseminating insecticides such as Dursban and Ronnel brand insecticides manufactured by The Dow Chemical Company. The formulation comprises an oxidizing agent, a non-halogenated polyepoxide resin as fuel and binder, an auxiliary fuel such as thiuram disulfide, a cooling additive, and an effective amount of the insecticide to be disseminated.

7 Claims, No Drawings PYROTECIINIC DISSEMINATING SYSTEM BACKGROUND OF THE INVENTION The present application is a continuation-in-part of a parent application of Ser. No. 709,916 filed Mar. 4, 1968, now abandoned, by Erwin M. Jankowiak, Earl T. Niles and George A. Lane.

The area of art to which this invention relates is that involving pyrochemical dissemination of pesticides, and particularly insecticides, by pyrochemical means.

Presently, it is common practice to disseminate insecticides by the use of complex and expensive machinery which generate fogs or sprays. Many areas, such as swamps or extremely mountainous terrain are inaccessible to wheeled vehicles bearing such machinery. Aircraft can be fitted with machinery for spraying but air coverage is not always thorough. In addition, airborne sprays do not sift easily through the canopy of trees and vegetation which shield the waters of swampy terrain. Such waters therefore remain substantially inaccessible to airborne sprays and continue to exist as prime breeding places for mosquitoes and other pestilential forms of life. Further, airplane spraying, as with other present forms of dissemination, is quite expensive. For the reasons enumerated above, it is advantageous to employ a pyrochemical munition such as the type revealed in this disclosure. Such a device has several advantages in that it is relatively inexpensive to manufacture if composed of the ingredients disclosed herein, can be used any place that is accessible to man, and does not require complex, cumbersome and expensive dissemination devices.

Heretofore, pyrochemical devices have been employed to disseminate fogs, gases, light producing flare components, and other chemical agents. Many such devices suffer from the disadvantage that they are difficult and expensive to make. Ordinarily, in conventional applications the agent to be disseminated is compacted with a mixture of carbohydrates or sulfur, and an inorganic oxidizing agent. Such compaction is very hazardous in that the composition is sensitive to shock and may detonate during the preparation of the munition. In addition, the machinery employed is expensive and the compaction process is slow. Also, using such fabrication procedures the ingredients often give off powders or dusts which create health problems and poor working conditions.

The invention disclosed herein surmounts the problems outlined hereinabove. Instead of employing high pressures to compact the ingredients as is done currently, the present invention provides a castable formulation containing a liquid non-halogenated polyepoxide resin and curing agent as binder fuel, an insecticide to be disseminated, an inorganic oxidizing agent, a gas generating compound and an easily oxidized auxiliary fuel. The solid ingredients are blended into the liquid system of epoxy resin and curing agent until a homogenous mixture is obtained. This mixture will generally be fluid or plastic in nature, and can be easily cast or extruded to a desired shape. The formed, i.e., shaped, product is cured to produce a solid product. On attaching a suitable ignition source, such as the commonly used grenade ignition fuse, to the resulting cured grain, a munition is formed which can be ignited by the fuse to disseminate an insecticide. Because the particles produced on dissemination are less than microns in size, the present invention also provides the additional advantage and utility of being suitable for fumigation purposes.

It is a principal object of the present invention to provide a novel pyrotechnic composition for the dissemination of insecticides.

It is a further object to provide a composition which before curing can be easily cast or extruded into a predetermined shape or form, and is relatively safe when being manufactured, because the high pressures encountered in compaction as well as the dusts formed in the use of such a technique are not present.

Another object of the present invention is to provide a pyrotechnic formulation which permits convenient dissemination of pesticides into areas not readily reached by presently available spraying equipment and processes.

DESCRIPTION OF THE INVENTION The invention is a pyrochemical composition comprising an inorganic oxidizing agent; a polyepoxide resin having a functionality in excess of l and less than about 3, as fuel and binder; a curing agent for said binder consisting of an amine, a mono or dicarboxylic acid or acid anhydride thereof; a gas generating cooling agent; an auxiliary fuel; and an effective amount of an insecticide to be disseminated. More specifically, the invention comprises from about 15 to 35 percent by weight of an alkali metal or ammonium nitrate, -chlorate, -perchlorate or mixtures thereof; from about 12 to about 25 per cent by weight of a resin of the type set forth directly hereinbefore, from about 0.1 to about 10 per cent by weight of curing agent, from about 5 to 20 per cent of a cooling agent, from about 5 to 20 per cent of an auxiliary fuel, and the balance an effective amount of an insecticide to be disseminated.

The term effective quantities" as used herein to designate the amount of insecticide to be disseminated means that amount of insecticide which would normally be employed by one skilled in insecticide dissemination to accomplish a predetermined or desired level of treatment or activity.

The term epoxide functionality refers to the average number of epoxy groups contained in the average polyepoxide molecule. This value should be greater than 1, preferably greater than 1.5 and can be obtained by dividing the average molecular weight of the polyepoxide by the epoxide equivalent weight.

If the polyepoxide material consists of a single compound and all of the epoxy groups are intact, the epoxide functionality will be integers such as 2,3,4, and the like. However in the case of polymeric polyepoxides, many of the materials may contain some of the monomeric monoepoxides or have some of their epoxy groups hydrated or otherwise reacted and/or contain macromolecules of somewhat different molecular weight so the epoxy equivalency may be quite low and containing fractional values. The polymeric material may, for example, have an epoxy equivalency of 1.5, 1.8, 2.5, and the like.

The polyepoxides which can be employed as binderfuels may be aliphatic, cycloaliphatic, aromatic or heterocylic. Generally, the polyepoxides are nonhalogenated. Suitable aliphatic polyepoxides include, for example, aromatic glycidyl ethers such as the diglycidyl ether of bisphenol A, and disulfide-containing aromatic glycidyl ethers such as [p-(2,3-epoxypropoxy)-phenyl] disulfide which corresponds generally to the structural formula:

Aliphatic glycidyl ethers such as glycerine glycidyl ethers (e.g., the diglycidyl ether of glycerine) are also employed as the binder fuel. Other polyepoxides include sulfide-containing aliphatic glycidyl ethers such as l,2,4-tris(2-(2,3-epoxypropylthio)ethyl)cyclohexane and 3,3-(ethylenebis(thioethylene)bis(7- oxabicyclo[4. l .0] cycloheptane.

To achieve the optimum in castability of the binderfuels, it is desirable to copolymerize the polyepoxide with a liquid low molecular weight polysulfide resin. The polysulfide resins also increase the efficiency of combustion and agent dissemination. Suitable polysultide resins correspond generally to the structural formula:

and are generally prepared by reacting dichloroethyl formal with sodium polysulfide and a chlorinated hydrocarbon such as trichloropropane or chlorinated ethane. The molecular weight of the polysulfides is within the range of from about 500 to about 4,000. Viscosity of the polysulfides is less than about 60 poise (measured at l60 F.). Suitable polysulfide resins which are commercially available include the LP-3 and LP-8 brand of polysulfide resins manufactured by the Thiokol Corporation.

Generally, if used, the polysulfide resin comprises up to a maximum of about 50 per cent of the binder-fuel weight and, preferably up to a maximum of about 28 per cent. This corresponds to a maximum of about 10 per cent and preferably about 5 per cent of the total formulation weight of the pyrotechnic composition.

The following compounds are illustrative of those materials which can be employed in the present invention as auxiliary fuels; thiourea, tetramethylthiuram disulfide, tetraethylthiuram disulfide, monoaminoguanidinium nitrate, cliaminoguanidinium nitrate, triaminoguanidinium nitrate, ethylenebisaminomonoguanidinium)dinitrate, l-amino-2,5-hydrazinetriazol nitrate, l-amino-2,5-hydrazinotriazol dinitrate, thiosemicarbazide, ethylenebis(thiosemicarbazide), thiocarboxyhydrazide, aminonitroguanidine and dithiobiurea.

Compounds suitable for use as cooling additives are those materials which upon heating liberate carbon dioxide, nitrogen, sulfur or mixtures thereof, including, for example, alkali metal acid carbonates, ammonium acid carbonates, guanidine carbonate, oxamide, oxalic dihydrazine and urea oxalate.

Compounds employed as curing agents include amines and dicarboxylic acids and their respective acid anhydrides. Typical amines include the aliphatic amines such as ethylene diamine, ethylamine, isopropylamine, n-butylamine, isobutylamine, 2- ethylhexylamine, and cyclohexylamine. Representative carboxylic acids include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, maleic acid and itaconic acid. Typical polycarboxylic acid anhydrides include succinic anhydride, maleic anhydride, itaconic anhydride and phthalic anhydride.

The amount of curing agent and total quantities of binder components to be employed in preparing a particular munition within the composition range disclosed herein are dependent to a large extent of the type of handling properties desired in the blended munition, temperature of mixing and blending, the length and temperature of cure to be employed and the amount of agent present.

To illustrate, it has been found in formulations containing a binder of an aromatic disulfide containing polyepoxide resin cured with maleic anhydride that when the binder weight is greater than about 25 per cent of the formulation, the maleic anhydride curing agent should comprise from about 20 to about 50 per cent of the total binder while in formulations containing less than 20 per cent binder, the maleic anhydride should be from about 26 to about 50 per cent of the binder.

Fabrication of the composition is accomplished by blending the insecticide, oxidizer (e.g., KCl0 auxiliary fuel, gas generator and curing agent into the liquid polyepoxide resin at room temperature until a homoge neous mass is obtained.

The resulting blend is cast or extruded into a mold of predetermined configuration to provide a propellent grain. The curing of the resulting blend preferably is conducted by allowing the so-cast grain to reside in the mold at room temperature for from about 24 to about 48 hours. Following this step, the product is heated gently at about 50 C. C., for from about 4 to about 6 hours, after which the product can be fitted with an igniter as is common in solid propellents, or otherwise ignited when used.

The invention surmounts previous fabrication problems of safety and health because the oxidizer and agent to be disseminated are dispersed throughout a liquid media which can be easily extruded or cast by presently available processes. Thus, the unsafe high pressures and shock of compaction are avoided and the unhealthy dust laden atmosphere generally accompanying the compaction of powdery substances is substantially reduced if not eliminated.

DESCRIPTION OF PREFERRED EMBODIMENTS A preferred embodiment of the present invention consists (on a weight basis) of from about 20 to about 35 per cent of an insecticide to be disseminated, from about 18 to about 28 per cent oxidizer, from about 13 to about 20 per cent of a non-halogenated sulfidecontaining polyepoxide resin as binder-fuel, from about 1 to about 10 per cent of a curing agent, from about 10 to about 20 per cent of a thiuram type compound as an auxiliary fuel, and from about 10 to about 20 per cent of a reaction cooling additive (e.g., sodium acid carbonate). Preferably, the auxiliary fuel is an alkylthiuram disulfide corresponding to the formula [R2NCS] S where the R group is composed of either straight or branched chain alkane hydrocarbons of from one to 10 carbon atoms. The tetraethyland tetramethylthiuram disulfides, known in the art as thiuram, are particularly suitable for use in the present invention.

This composition generally is suited to the dissemination of insecticides, and because of its low combustion temperature is especially suitable where Dursban brand insecticide (0,0-diethyl-0,3,5,6-trichloro-2-pyridyl phosphorothioate) or Ronnel brand insecticide (0,0-

dimethy1-0,[ 2 ,4,5-trichlorophenyl 1 phosphorothioates) is to be disseminated.

EXAMPLE I About 14.8 parts by weight of a liquid nonhalogenated, aromatic disulfide-containing polyepoxide resin, 5.3 parts by weight of maleic anhydride, and about 13.3 parts by weight of tetramethylthiuram disulfide were mixed until homogeneous. The polyepoxide resin corresponded generally to the structure About 13.3 parts by weight of sodium bicarbonate, 20.0 parts by weight of potassium chlorate, and 33.3 parts by weight of Dursban brand insecticide (a product of The Dow Chemical Company) were added and the mixture was agitated until a homogeneous mass was obtained. The entire mixing operation was carried out at about 20 C.

The resulting mass was cast into a cylindrical munition mold and cured at 20 C. for about 30 hours. Following this step, the product was cured at 55 C. for 5 hours. The resulting product was a cylindrical, end burning grain weighing grams.

Combustion studies were carried out on samples of the product. The studies indicated a burning time of about 5 seconds per 10 grams of product and a combustion temperature range of from about 275 C. to about 400 C. The efficiency of agent dissemination was about 50 per cent.

To demonstrate the utility of the composition in disseminating insecticide under actual operating conditions, field studies were carried out. Ten gram end burning munition grains were ignited, thereby forming a coherent cloud of insecticide about 50-60 feet from the line of fire. The cloud was carried along by the wind so that it passed through cages containing adult mosquitoes of the type Culex fatigans and Aedes aegypti set 4 to 5 feet above the ground. The cloud also passed over pans one-fourth to one-half full of water setting upon the ground, and containing larvae of the above named types of mosquitoes. The amount of munitions employed in separate studies was selected so that, upon firing, a cloud would be produced which was calculated on a theoretical basis to provide an insecticide density of either about 0.2 pounds per acre or about 0.05 pounds per acre. The results of this study are summa- These test results demonstrate conclusively that Dursban brand insecticide can be effectively disseminated and its biological activity maintained by the pyrotechnic means of dissemination disclosed in the present application.

Other embodiments of the above-defined formulation also can be employed successfully. To illustrate, Applicant found that a munition with a dissemination efficiency of about per cent to about 60 per cent was produced by a fuel munition grain comprising about 25.0 parts by weight of Dursban brand insecticide, about 22.4 parts by weight of potassium chlorate, about 16.5 parts by weight of the disulfide containing epoxy based resin, about 5.9 parts by weight of maleic anhydride, about 15.1 parts by weight of tetramethylthiuramdisulfide, and about 15.1 parts by weight of sodium acid carbonate. This formulation burned at a temperature of about 300 C. to about 400 C., and at a rate of about 5 to about 6 seconds per every 10 grams of munition employed.

In yet another embodiment, about 15 parts by weight of Dursban brand insecticide, about 25.5 parts by weight of potassium chlorate, about 18.7 parts by weight of a liquid aromatic disulfide-containing epoxy based resin, about 6.8 parts by weight of maleic anhydride, about 17.0 parts by weight of tetramethylthiuramdisulfide, and about 12.0 parts by weight of sodium acid carbonate were employed. The blending and curing process used to make the munition was similar to that employed in Example 1. This cured munition product upon ignition burned at a combustion rate of about 5 seconds for every 10 grams of munition employed. The insecticide was disseminated at a reaction temperature of about 275 C. to about 400 C. The munition developed an efficiency of about 24 per cent to about 45 per cent.

In a manner similar to that defined for the foregoing examples, other pyrotechnic disseminating munitions containing pesticides such as Ronnel brand insecticide, for example, can be fabricated within the disclosed operating parameters disclosed above.

EXAMPLE II tion, the disseminating efficiency is less than about 10 What is claimed is:

1. A pyrotechnic disseminating formulation comprising on a weight basis:

a. from about to about 35 per cent of an oxidizing agent selected from the group consisting of an alkali metal or ammonium nitrate, chlorate, perchlorate and mixtures thereof,

b. from about 12 to about 25 per cent of a nonhalogenated polyepoxide resin having a functionality greater than 1 and less than about 3, said polyepoxide resin being selected from the group of the glycidyl ether of bisphenol A, bis[p-(2,3-epoxypropoxy)-phenyl disulfide], glycerine glycidyl ether, 1,2,4-tris (2-(2,3-epoxypropylthio)ethyl) cyclohexane and 3,3 (ethylenebis(thioethylene)bis(7-oxabicyc1o)4.1.0- )cycloheptane;

c. from about 0.1 to about 10 per cent of an amine or a dicarboxylic acid or dicarboxylic acid anhydride as curing agent, said curing agent being selected from the group of ethylene diamine, ethylamine, isopropylamine, n-butylamine, isobutylamine, Z-ethylhexylamine, cyclohexylamine, oxalic acid, malonic acid, succinic acid, maleic acid, itaconic acid, succinic anhydride, maleic anhydride, itaconic anhydride and phthalic anhydride;

. from about 5 to about per cent of a gas generating cooling agent selected from the group consisting of alkali metal acid carbonates, ammonium acid carbonates, guanidine carbonate, oxamide, oxalic dihydrazine and urea oxalate;

e. from about 5 to about 20. per cent of auxiliary fuel,

selected from the group consisting of thiourea, tetramethylthiuram disulfide, tetraethylthiuram disulfide, monoaminoguanidinium nitrate, diaminoguanidinium nitrate, triaminoguanidinium, ethylenebis(aminomonoguanidinium)dinitrate, l-amino-2,S-hydrazine-triazol nitrate, l-amino- 2,5hydrazine-triazol dinitrate, thiosemicarbazide, ethylenebis(thiosemicarbazide), thiocarboxyhydrazide, aminonitroquanidine and dithiobiurea; and

f. the balance of an insecticide selected from the group of 0,0-dieth'yl-O,3,5,6-trichloro-2-pyridyl phosphorothioate and 0,0-dimethyl-O[2,4,5- trichlorophenyl] phosphorothioate.

2. The composition of claim 1 wherein on a weight basis from about 18 to about 28 per cent is oxidizer, from about 13 to about 20 per cent is a nonhalogenated, sulfide-containing polyepoxide resin as binder-fuel, from about 1 to about 10 per cent is curing agent, from about 10 to about 20 per cent is an auxiliary fuel, and from about 10 to about 20 per cent is a cooling additive.

3. The composition of claim 1 having: from about 15 to about 35 per cent of potassium chlorate as oxidizing agent; from about 1 to about 10 per cent of maleic anhydride as curing agent for the binder-fuel; from about 10 to about 19 per cent sodium acid carbonate as cooling agent; and from about 10 to about 20 per cent of tetramethylthiuramdisulfide as auxiliary fuel.

4. The composition of claim 1 wherein the polyepoxide is copolymerized with a low molecular weight polysulfide resin of the formula H(SCH CH OCH- OCH CH S),, wherein x is an integer sufficient to provide a resin having a molecular weight of from about 500 to about 4,000.

5. The composition of claim 4 wherein the molecular weight of the polysulfide is within the range of from about 500 to .about 4,000 and the viscosity at l60 F. is less than about 60 poise.

6. The composition of claim 4 wherein the polysulfide resin comprises a maximum of about 50 weight per cent of the binder fuel.

7. The composition of claim 6 wherein the polysulfide resin comprises up to about 28 per cent of the binder fuel and corresponds to a maximum of about 10 per cent of the total weight of the composition. 

1. A PYROTECHINIC DISSEMINATING FORMULATION COMPRISING ON A WEIGHT BASIS: A. FROM ABOUT 15 TO ABOUT 35 PER CENT OF AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF AN ALKALI METAL OR AMMONIUM NITRATE, CHLORATE, PERCHLORATE AND MIXTURES THEREOF, B. FROM ABOUT 12 TO ABOUT 25 PER CENT OF A NON-HALOGENATED POLYEPOXIDE RESIN HAVING A FUNCTIONALITY GREATER THAN 1 AND LESS THAN ABOUT 3, SAID POLYEPOXIDE RESIN BEING SELECTED FROM THE GROUP OF THE GLYCIDYL ETHER OF BISPHENOL A, BIS(P-(2,3-EPOXYPROPOXY)-PHENYL DISULFIDE),GLYCERINE GLYCIDYL ETHER, 1,2,4-TRIS (2-(2,3-EPOXYPROPYLTHIO)ETHYL) CYCLOHEXANE AND 3,3''-(ETHYLENEBIS(THIOETHYLENE)BIS(7OXABICYCLO)4.1.0)CYCLOHEPTANE; C. FROM ABOUT 0.1 TO ABOUT 10 PER CENT OF AN AMINE OR A DICARBOXYLIC ACID OR DICARBOXYLIC ACID ANHYDRIDE AS CURING AGENT, SAID CURING AGENT BEING SELECTED FROM THE GROUP OF ETHYLENE DIAMINE, ETHYLAMINE, ISOPROPYLAMINE, NBUTYLAMINE, ISOBUTYLAMINE, 2-ETHYLHEXYLAMINE, CYCLOHEXYLAMINE, OXALIC ACID, MALONIC ACID, SUCCINIC ACID, MALEIC ACID, ITACONIC ACID, SUCCINIC ANHYDRIDE, MALEIC ANHYDRIDE, ITACONIC ANHYDRIDE AND PHTHALIC ANHYDRIDE; D. FROM ABOUT 5 TO ABOUT 20 PER CENT OF A GAS GENERATING COOLING AGENT SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL ACID CARBONATES, AMMONIUM ACID CARBONATES, GUANIDINE CARBONATE, OXAMIDE, OXALIC DIHYDRAZINE AND UREA OXALATE; E. FROM ABOUT 5 TO ABOUT 20 PER CENT OF AUXILIARY FUEL, SELECTED FROM THE GROUP CONSISTING OF THIOUREA, TETRAMETHYLTHIURAM DISULFIDE, TETRAETHYLTHIURAM DISULFIDE, MONOAMINOGUANIDINIUM NITRATE, DIAMINOGUANIDINIUM NITRATE, TRIAMINOGUANIDNIUM, ETHYLENEBIS(AMINOMONOGUANIDINIUM)DINITRATE, 1-AMINO2,5HYDRAZINE-TRIAZOL NITRATE, 1-AMINO-2,5HYDRAZINE-TRIAZOL DINITRATE, THIOSEMICARBAZIDE, ETHYLENEBIS(THIOSEMICARBAZIDE), THIOCARBOXYHYDRAZIDE, AMINONITROQUANIDINE AND DITHIOBIUREA, AND F. THE BALANCE OF AN INSECTICIDE SELECTED FROM THE GROUP OF 0,0-DIETHYL-0,3,5,6-TRICHLORO-2-PYRIDYL PHOSPHOROTHIOATE AND 0,0-DIMETHYL-0(2,4,5-TRICHLOROPHENYL) PHOSPHOROTHIOATE.
 2. The composition of claim 1 wherein on a weight basis from about 18 to about 28 per cent is oxidizer, from about 13 to about 20 per cent is a non-halogenated, sulfide-containing polyepoxide resin as binder-fuel, from about 1 to about 10 per cent is curing agent, from about 10 to about 20 per cent is an auxiliary fuel, and from about 10 to about 20 per cent is a cooling additive.
 3. The composition of claim 1 having: from about 15 to about 35 per cent of potassium chlorate as oxidizing agent; from about 1 to about 10 per cent of maleic anhydride as curing agent for the binder-fuel; from about 10 to about 19 per cent sodium acid carbonate as cooling agent; and from about 10 to about 20 per cent of tetramethylthiuramdisulfide as auxiliary fuel.
 4. The composition of claim 1 wherein the polyepoxide is copolymerized with a low molecular weight polysulfide resin of the formula H(SCH2CH2OCH2OCH2CH2S)x, wherein x is an integer sufficient to provide a resin having a molecular weight of from about 500 TO about 4,000.
 5. The composition of claim 4 wherein the molecular weight of the polysulfide is within the range of from about 500 to about 4, 000 and the viscosity at 160*F. is less than about 60 poise.
 6. The composition of claim 4 wherein the polysulfide resin comprises a maximum of about 50 weight per cent of the binder fuel.
 7. The composition of claim 6 wherein the polysulfide resin comprises up to about 28 per cent of the binder fuel and corresponds to a maximum of about 10 per cent of the total weight of the composition. 